Machine for sharpening mowing machine cutters



Nov. 8, 1932. J. NOBS MACHINE .FQR SHARPENING MOWING MACHINE CUTTER-5 Filed May 12, 1931 Patented Nov. 8, 1932 PATENT JAKOIB NOBS, OF THUN, SWITZERLAND MACHINE FOR SHARIPENING MOWING-MACHINE GUTTERS Application filed May 12, 1931, Serial No.

This invention relates to machines for sharpening mowing-machine cutters, and has for its object to provide an improved construction comprising a rotary grinding disc which, besides rotating, is reciprocated in its own plane and has at one side a conical face corresponding in conicity to the angle of the cutting edges of the teeth of a mower-cutter so that when the latter bears with two teeth against the cutter the two adjacent cutting edges of the two teeth are ground simultaneously along their entire length.

According to a feature of the invention the grinding disc is mounted to float on a shaft which is guided to move axially against a spring in a hollow shaft which is rotated by gearing comprising a rotating belt or the like and is simultaneously moved up and down along a vertical guide by means of a connecting-rod, crank-pin and a driving wheel.

According to another feature of the invention a rod serving to reciprocate the slide vertically has at one end a screw thread and,

5 passes freelythrough a link situated between two nuts on the threaded end, for enabling the magnitude of the stroke of the slide and disc to be varied by adjusting one of said nuts.

Preferably, the link is adjustable in height and detachably connected with the slide, and

the latter after being disengaged from the connecting-rod can be fixed at any desired height.

' Conveniently, an axle is fixed on the frame at the side of said disc, on which axle a holder for a. mower-cutter is guided to move longitudinallyand is mounted to swing.

Other features of the invention will be described hereinafter and pointed out in the claims. j 7 One embodiment of the invention is diagrammatically illustrated by way of example in the accompanying-drawing, wherein Figure-1 is a vertical longitudinal section taken on the line 1-1 in Figure 2 showing one form of sharpening machine according to the invention,

. Figure 2 is a plan thereof,

536,851, and in Switzerland. May 16, 1930.

Figure 3 is an end elevation the left hand of Figure 1, and

Figure 4 is a side elevation illustrating the grinding operation. Y

Like reference characters designate like parts throughout the several views.

Referring to the drawing, a horizontal rectangular frame 2 having feet 1 carries a stand 4 at oneend. Two horizontal shafts V 5 and 6 are journaled on the frame 2 towards its other end; these shafts are positively geared together by gear wheels 7, 8, and the shaft 5 can be rotated manually'by a crank handle or driven by a motor and belt. The shaft 6 transmits its rotation by a belt drive comprising a pulley 10, beltll and pulley 12 to a hollow shaft 13 carrying the pulley 12. This shaft 13 is journaled in two bearings 14 on a slide 15 movable up and down in two vertical guides 16 on the stand 4..

In order to move the slide automatically up and down while the shaft 13 is rotating it is operatively connected with a crank-pin 21 of the gear wheel 7 by mechanism comprising a double-ended lever 18 fulcrumed at 17 7 on the frame 2 and two links 19 and 20 pivoted to its end, the link 20 being pivoted to the pin 21.

The'link or-rod 19 has its upper end 22 screw-threaded and passes freely through one arm of a bracket 25 situated betweentwo nuts 23 and 24 on its threaded end; theother arm of this bracket 25 is pivoted by a removable pivot pin 26 to a pair of eyes 27 on the slide. The lowest position of the slide 15 5 is limited by a stop or pin 29 extending from the stand 45 into the path of the eyes 27. After removing the pin 26 and turning the as seen from bracket 25 the slide 15 can be moved by hand to anydesired height and be fixed by a set- 90. screw 30 in the stand 4. The object of fixing the slide 15 is to enable a part of a cutting edge, e. g. a notch, that has to be ground away a considerable depth to be held for an abnormally long time in contact with the grinding disc or wheel described hereinafter. V

A shaft 31 is axially movable in the hollow shaft 13 and carries on its upper end in Figure 2 a grinding disc or wheel 32 whereof the outer face is coincal to a degree corresponding to the angle of the teeth of a mower-cutter. When the cutter presses on the conical fact of the disc the latter can recede against the action of a coil spring 33 that is accommodated in the hollow shaft 13 and loads the shaft 31.

For holding a mowercutter to be sharpened a holder 36 is pivotally mounted on brackets 34 by means of a fixed axle 35 on the same side of the frame 2 as the grinding disc, on which holder the cutter. to be ground can be placed. shown in itslower position in which the cutter, not shown, can be conveniently placed on it and removed.

This holder 36 comprises a substantially U-shaped frame having a broad end portion having a downwardly opening U-shap-ed recess in the middle. The end of the left-hand limb shown in Figure 2 carries a freely rotatable but axially non-displaceable nut 37 into which the threaded end of .the axle 35 extends. By turning the nut 37 it is therefore possible to shift the holder 36 with the cutter on it longitudinally in relation to the disc 32 and so to adjust it, for example, that the disc contacts with both of the edges next adjacent to it equally or with different degrees of pressure or with only one of them.

A rod 38 having a right-angle bend is pivotally mounted at one end on the limb of the holder 36 carrying the nut 37; the other end of this rod 38 is screw-threaded and extends into a nut 39 which is rotatable but axially non-displaceable in an arm 40 which is rotatable about its longitudinal axis on the frame 1; this nut 39 and rod 38 thus constitute part of a pivotal connection or variable length between the cutter holder and the frame .2. By turning the nut 39 the holder 36 can be set at a more or less steep angle to the plane of the disc 32.

The holder 36 is provided on its inner side with a longitudinal groove 41 for receiving the beam or bar carrying the cutter blade. In

. order that beams of various widths may be placed on the groove 41 in a position rectangular to the path of the disc 32, the holder 36 carries a set-screw 42 in the middle of tis end member. On this ground the groove is slotted as shown in Figure3 for receiving the heads of rivets fixing the cutter blades on the beam. At the rear side of the holder 36 an arm 44 is mounted to swing about a pivot pin 45 and to move endwise. The arm 44 carries at or towards its free end two 'clamping'springs 46 having bent ends extending away from one another, with which the cutter can be secured against falling off the holder after the arm 44 has been swung to one side or the other about its pivot 45.

- For grinding a mower-cutter the latter is so placed by theholder36 in relation to the discj 32, as indicated in Figu're4, that the In Figure 2 the holder 36 is' middle of a gap between two teeth is in line with the vertical axial plane of the cutter. If the cutter is then pressed against the conical face of the disc and the latter is rotated the disc will then grind simultaneously the two cutting edges of the two adjacent teeth lying next to it. In consequence of the vertical .reciprocatory movementof the disc the two cutting edges will be ground uniformly and rectilinearly along their entire length. The conical side face of the disc achnits .of the cutting edges of the blade being ground right'up to the point where they. meet, that is to say to the bottom of the gap, where, as is known, they are subjected to the greatest amount of wear.

By screwing the nut 23 down the rod 19 it is possible to vary the stroke of the slide 15 and disc- 32 corresponding to the requirements of each case. As the disc, when rotating, continuously changes its vertical position the cutting edges are never ground continuously at. one and the same spot andconsequently are not unduly heated by the grinding operation whereby their hardness might be impaired. I

The described machine is very simple to operate. When driven manually the crankhandle can be turned by the right hand whilst the left attends to the adjustment of the cutterholder, as to its longitudinal position and its slant, by'turning the nuts 37 and 39. Also a cutter. can be placed on the holder 36, adjustedvin position thereon, and removed therefrom readily and quickly and without the use of tools.

The invention is not restricted to the precise constructional details enumerated.

1.- A machine for sharpening mower-cutters comprising in combination a frame, a grinding disc havinga conical face mounted to rotate thereon, means for rotating the grinding disc and simultaneously reciprocating it in'its own plane, and a holder for supporting a cutterjagainst the said conical face whereof the conicity corresponds to the angle between thecutting edges of two adjacent teeth of the cutter. V

2. A machine for sharpening mower-cutters comprising in combination a frame,- a grinding disc having a conical face mounted to rotate thereon, means for rotating the grinding disc, means for, simultaneously reciprocating the disc in its own plane, means for varying the reciprocatory stroke of the disc, and a holder for supporting a cutter against the said conicalface whereof the conicity corresponds to the angle between the cutting edges of two adjacent teeth of the cutter.

3. A machine for sharpening mowercutters comprising in combination a frame,-a slide thereon, a shaft journaled in said slide, a grinding disc having a conical face carried by said shaft, a holder pivoted on said frame and arranged to hold a cutter against said degree of justably connected to said bracket, and means for reciprocating said link in the direction of its length.

4. A machine for sharpening mower-cutters comprising in combination a frame, a slide thereon, a shaft j ournaled in said slide, a grinding disc having a conical face carried by said shaft, a holder on said frame arranged to hold a cutter against said conical face whereof the conicity corresponds'to the angle between the cutting edges of two adj acent teeth of the cutter, a bracket pivotally and detachably carried by said slide, a link extending in the direction of movement of the slide and adjustably connected to said bracket, and means for reciprocating said link endwise during the rotation of said shaft.

5. A machine for sharpening mower-cutters comprising in combination a frame, a slide movable thereon, a shaft journaled in said slide, a grinding disc having a conical face carried by said shaft, means for rotating said shaft, an axle fast on said frame, and a holder for a cutter mounted to swing about and move alongaxle and hold the cutter against said conical face whereof the degree of conicity corresponds to the angle between the cutting edges of two adjacent teeth of the cutter.

6. A machine for sharpening mower-cutters comprising in combination a frame, a slide thereon, a shaft journaled in said slide, a grinding disc having a conical face carried by said shaft, means for rotating said shaft,

a holder pivoted on said frame for supporting a cutter against the said conical face whereof the conicity corresponds to the angle between the cutting edges of two adjacent teeth of the cutter, and adjustable means for said frame for supporting a cutter against said conical face whereof the degree of conicity corresponds to the angle between the cutting edges of two adjacent teeth of the cutter, and detachable adjustable means for holding the holder at various angles with the general plane of said disc.

8. A machine for sharpening mower-cut ters comprising in combination a frame, a grinding disc having a conical face mounted to rotate thereon, and a holder for supporting a cutter against said conical face whereof the conicity corresponds to the angle between the adjacent cutting edges of two adjacent teeth of the cutter, which holder is of U-shape with the free ends of the limbs of the U pivoted on the frame, and the end memher of which U has a stepped groove for receiving a cutter beam, and a device for fixing the beam in said groove in position rectangular to the path of the grinding disc.

9. A machine for sharpening mower-cutters comprising in combination a frame, a grinding disc having a conical face mounted to rotate and to reciprocate in'its own plane thereon, means for rotating and simultaneously reciprocating said disc, a U-shaped holder pivoted by the free ends of its limbs on the frame for supporting a cutter against said conical face whereof the conical angle corresponds to the angle between the adjacent cutting edge of two adjacent teeth of the cutter, an arm mounted to swing and to move endwise on the end member of said holder, and clamping springs on said arm for holding a cutter in position on the holder.

10. A machine for sharpening mower-cutters comprising in combination a frame, a

slide movable vertically thereon, a hollow shaft j ournaled on said slide, a spring in said shaft, a disc having a conical grinding face carried by said shaft and pressed by said spring, means for rotating said shaft and said disc, means for simultaneously reciprocating said slide, a U-shaped holder pivoted by the free ends of its limbs on the frame for supporting a cutter against said conical face against the action of said spring, means for securing the cutter in position on the holder, and means for swinging the holder towards and away from said disc.

I J AKOB NOBS. 

